Question

package com.donateblood.blooddonation;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;

import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;

import java.util.ArrayList;
import java.util.List;

import butterknife.ButterKnife;
import butterknife.InjectView;

/**
 * Created by YouCaf Iqbal on 4/6/2016.
 */
public class MainGUI extends AppCompatActivity {
    public static ArrayList<DonorPerson> Donors = new ArrayList<DonorPerson>();
    @InjectView(R.id.findppl) Button _findButton;
    GPSTracker gps;
    String bloodgroup=null;
    private double latitude;
    private double longitude;
    DB db; String test="";
    DBCursor cursor;
    DBCollection collection;
    Database dataobj = new Database();
    ArrayList allPPLlat = new ArrayList();
    ArrayList allPPLlong = new ArrayList();
    ArrayList allPPLNumbers = new ArrayList();
    ArrayList allPPLNames = new ArrayList();
    ArrayList allPPLImages = new ArrayList();
    ArrayList allPPLEmails = new ArrayList();
    ArrayList SelectedPPLlat = new ArrayList();
    ArrayList SelectedPPLlong = new ArrayList();
    public Spinner mySpinner;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.maingui);
        ButterKnife.inject(this);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        Spinner spinner =(Spinner) findViewById(R.id.spinner);
        String[] list = getResources().getStringArray(R.array.blood_type);
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,R.layout.spinner_layout,R.id.txt,list);
        spinner.setAdapter(adapter);
        _findButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                getCurrentLatLong();
                dbAsync thrd = new dbAsync();
                thrd.execute();
            }
            //distance=Distance(lablat, lablong, curlat, curlong);
        });
    }
    public void getCurrentLatLong(){
        gps = new GPSTracker(MainGUI.this);
        if (gps.canGetLocation()) {
            latitude = gps.getLatitude();
            longitude = gps.getLongitude();
        }
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if(item.getItemId()==android.R.id.home){
            finish();
        }
        return super.onOptionsItemSelected(item);
    }


    public class dbAsync extends AsyncTask<Void,Void,Void>{
        private ProgressDialog pDialog;

        @Override
        protected Void doInBackground(Void... voids) {
            getOtherLatLong();
            return null;
        }

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(MainGUI.this);
            pDialog.setMessage("Searching people nearby...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(true);
            pDialog.show();
        }

        @Override
        protected void onPostExecute(Void aVoid) {

            super.onPostExecute(aVoid);
            pDialog.dismiss();
            Intent intent = new Intent(getApplicationContext(), PeopleList.class);
            startActivity(intent);
           // Toast.makeText(getBaseContext(), "Near by latitudes "+SelectedPPLlat, Toast.LENGTH_LONG).show();
           // Toast.makeText(getBaseContext(), "Near by longitudes "+SelectedPPLlong, Toast.LENGTH_LONG).show();
        }
    }

    public void getOtherLatLong() {
        db = dataobj.getconnection();
        collection = db.getCollection("UserDetails");
        //mySpinner=(Spinner) findViewById(R.id.spinner);
        //bloodgroup = mySpinner.getSelectedItem().toString();
       // BasicDBObject whereQuery = new BasicDBObject();
        //whereQuery.put("employeeId", 5);
        cursor = collection.find();
        while (cursor.hasNext()) {
            DBObject doc = cursor.next();
            // Lats longs used in the next for Loop for calculation distances
            allPPLlat.add(doc.get("lat"));
            allPPLlong.add(doc.get("long"));
            // All these other arraylists are used to store object of a donor person
            allPPLNumbers.add(doc.get("number").toString());
            allPPLNames.add(doc.get("Name").toString());
            allPPLImages.add(doc.get("image").toString());
            allPPLEmails.add(doc.get("email").toString());

        }

        for(int i =0;i<allPPLlat.size();i++){
           double Dist= Distance((double)allPPLlat.get(i),(double)allPPLlong.get(i),latitude,longitude);
            Dist=Dist/1000;
            if(Dist<20){
                Donors.add(new DonorPerson(""+allPPLNames.get(i)+"", ""+allPPLEmails.get(i)+"" ,""+allPPLNumbers.get(i)+"" ,""+allPPLImages.get(i)+""));
            }
        }
    }

    public double Distance(double lat1, double lon1, double lat2, double lon2) {
        double R = 6371.0; // km
        double dLat = (lat2 - lat1) * Math.PI / 180.0;
        double dLon = (lon2 - lon1) * Math.PI / 180.0;
        lat1 = lat1 * Math.PI / 180.0;
        lat2 = lat2 * Math.PI / 180.0;

        double a = Math.sin(dLat / 2.0) * Math.sin(dLat / 2.0) +
                Math.sin(dLon / 2.0) * Math.sin(dLon / 2.0) * Math.cos(lat1) * Math.cos(lat2);
        double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
        double d = R * c;
        return d * 1000; // return distance in m
    }
}

我在我的一个名为Donors的类中声明了一个名为MainGUI的静态自定义视图。每当显示列表并返回并重新打开列表时，相同的列表项将出现两次。我知道发生这种情况是因为列表项在我显示时再次添加到列表视图而不清除之前显示的所有数据项。我想要的是一种在重新打开列表时删除所有现有数据项的方法，以便在我再次访问它时不会重复这些项目。

public class PeopleList extends AppCompatActivity {


    @Override
    public void onBackPressed() {
       MainGUI.Donors.clear(); // Clear all the Donors after search
       // this.notifyDatasetChanged();
        super.onBackPressed();

    }
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.peoplelistview);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        populateListView();

    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if(item.getItemId()==android.R.id.home){
         //   MainGUI.Donors.clear(); // Clear all the Donors after search
            finish();
        }
        return super.onOptionsItemSelected(item);
    }

    private void populateListView() {
        ArrayAdapter<DonorPerson> adapter = new MyListAdapter();
        ListView list = (ListView) findViewById(R.id.DonorsListView);
        list.setAdapter(adapter);
    }

    private class MyListAdapter extends ArrayAdapter<DonorPerson> {
        public MyListAdapter() {
            super(PeopleList.this, R.layout.singlelistitemview,MainGUI.Donors);
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            // Make sure we have a view to work with (may have been given null)
            View itemView = convertView;
            if (itemView == null) {
                itemView = getLayoutInflater().inflate(R.layout.singlelistitemview, parent, false);
            }
            // Find the Donor to work with.
            DonorPerson currentPerson = MainGUI.Donors.get(position);
            //Set the Image of the Current Donor
            ImageView DonorImage = (ImageView)itemView.findViewById(R.id.image);
            //currentPerson.getImage();
            byte[] decodedString = Base64.decode(currentPerson.getImage(), Base64.DEFAULT);
            Bitmap decodedByte = BitmapFactory.decodeByteArray(decodedString, 0, decodedString.length);
            DonorImage.setImageBitmap(decodedByte);
            //imageView.setImageResource(currentPerson.getIconID());
            /* Fill the view
            ImageView imageView = (ImageView)itemView.findViewById(R.id.item_icon);
            imageView.setImageResource(currentCar.getIconID()); */

            return itemView;
        }
    }

}

Answer 1

只需对适配器使用clear方法，然后调用notifydatasetchanged方法。

_adapter.clear();
notifyDataSetChanged();

在创建适配器的类中执行此操作。

Answer 2

您可以尝试覆盖onDestroy（）方法。像这样的东西

cart.html

如何清除android中静态自定义列表视图的所有列表视图项？

2 个答案: